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A high-pressure system over San Antonio will result in dangerous record heat this week and possibly next week too, according to the National Weather Service.
West and southwest wind flows blowing across the Mexican plateau into South Texas are also helping to enhance the heat around the Alamo City, forecasters said.
A heat advisory is in effect through 9 p.m. on Wednesday for highs around 104 on Tuesday and 106 on Wednesday.
Highs of 100 or more are in the forecast through at least Saturday. Even hotter heat indices or "real feel" temperatures are expected.
Conditions may worsen on Wednesday, and an Excessive Heat Warning could replace the advisory.
"It will feel hot and dry initially before eventually becoming muggy and possibly even downright oppressive across the area," read a forecast discussion from the weather service.
"Multiple records in jeopardy of being broken," it added.
The very young, the elderly, and those with chronic conditions need to be checked on now by relatives, neighbors, and friends to make sure they can weather the heat wave comfortably in an air-conditioned room.
All residents are advised to dress in light colored and light weight clothing for the duration of the heat wave and drink plenty of fluids. Those working outdoors will need to take frequent breaks in the shade or in an air-conditioned room and also stay well hydrated.
Forecasters said such precautions are needed to prevent potentially deadly heat related illnesses, such a heat stroke.
